Recently, many distributed storage systems have been employed as an infrastructure in a business field in which high availability is desirable. For example, in client/server distributed storage systems, a client writes data into multiple servers or reads out data stored in a server. On the server side, multiple servers cooperate with each other, and store data in a redundant manner in preparation for a failure. For example, one server stores data, and another server stores the same data.
In such systems, when a failure occurs in a server, the redundancy of the data stored in a database of the failure server is reduced. Accordingly, when a failure occurs in a server, a recovery process is performed to restore the redundancy of the data in a database that had been managed by the failure server. In the recovery process, to suppress the reduction of the redundancy of the data, a server that stores the data (that is, a transfer-source server) transfers a copy of the data to a server that is newly selected (that is, a transfer-destination server). Thus, the redundancy of the data stored in the failure server is restored. Examples of a technique regarding a recovery process include a technique for enabling reduction in a time period in which data access is stopped when a failure occurs in a storage apparatus.
A technique of the related art is disclosed, for example, in Japanese Laid-open Patent Publication No. 2010-97385.